An electric field coupling scheme is known as a system in which power is wirelessly transmitted from a power transmission device to a power reception device. In such an electric field coupling scheme power transmission system, power is transmitted from an active electrode of the power transmission device to an active electrode of the power reception device via an electric field. In order to increase the power transmission efficiency, high-voltage transmission is performed by providing a voltage-boosting circuit in the power transmission device and a voltage-lowering circuit in the power reception device. An example of a power reception device is a mobile electronic appliance such as a cellular phone device and with the continuing progress being made in reducing the thickness and size of mobile electronic appliances in recent years, there have also been demands for reductions in the thickness and size of built-in components. Consequently, there is a need for high-withstand-voltage transformers designed to be small and have a low profile.
In Patent Document 1, an invention is disclosed that relates to a high-frequency transformer for high voltage and large current use. The high-frequency transformer according to Patent Document 1 has a configuration in which it is possible to connect primary windings and secondary windings of a plurality of transformers in series or in parallel with each other. With this configuration, the transformation ratio of the transformer can be adjusted and it is possible to handle both a case where low-voltage large-current high-frequency power is to be output and a case where high-voltage small-current high-frequency power is to be output.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-80011.
In the case of the electric field coupling scheme power transmission system, since there is a demand for reduction of the thickness of a power reception device as described above, there are restrictions on the space in which to arrange components to be built into the power reception device. Consequently, there is a problem in that noise generated by high-voltage portions and so forth affects low-voltage portions because it is not possible to secure a sufficient distance between the components. In Patent Document 1, a high-withstand-voltage transformer can be realized by adjusting the transformation ratio of the transformer, but the above-described problem cannot be solved.